ABA

Flat assumption-based argumentation (Bondarenko et al. 1997; Dung, Kowalski and Toni 2009), as the instance of ASPIC+ it is (Prakken 2010): strict rules, assumptions (assumption/1) as ordinary premises, contraries (contrary(Assumption, Contrary)) one way only, no preference, no other conflict (not even negation). A theory with defeasible rules, or an assumption a rule concludes (not flat), is refused: the semantics of non-flat ABA are those of sets of assumptions, which the arguments do not capture.